In compounding resins for such coating applications, resins containing carboxyl groups are added to enhance pigment wetting, gloss, and adhesion to substrates. In such polyblends of resins, a monomer is polymerized to the ends of polymer chains, the final resulting copolymer being a chain with sequences of different segments which are called block polymers.
There exists commercially available block polymers derived from the addition of various portions of monomers, such as ethylene oxide and propolyene oxide, to ethylenediamine.
In utilizing block copolymers as an adherent coating, three elements are normally analyzed in the formation of an adhesive bond. The three elements are the ability to wet the substrate, the spreading of the liquid over the surface of the substrate, and the capability of the liquid to harden into a solid material close in physical characteristics, such as Young's modulus to the substrate.
A wetting agent is any substance that increases the ability of liquid to displace air or other gas or water or another liquid from a solid surface. Such wetting agents influence three kinds of wetting; that is, spreading, adhesion and immersion. With regard to the present invention, it is preferable to have a wetting agent capable of excellent spreading characteristics as well as adhesion characteristics.
Spreading wetting is measured by the spreading coefficient. Spreading wetting occurs spontaneously only if the spreading coefficient is positive. For any liquid spreading over any surface, the spreading coefficient is calculated from the surface and interfacial tensions of liquids and surfaces involved.
Adhesion wetting is defined by how tightly a liquid adheres to a surface with which it was not previously in contact. Adhesional wetting is measured by the work required to separate a liquid from the wetted surface. If a liquid is wetting another liquid, surface and interfacial tensions are used to calculate the wetting constants, and if a solid surface is being wet, the contact angle is used for the calculation.
With regard to the ability of a liquid to harden into a solid material close to the substrate, chacteristics such as elastic modulus and coefficient of thermal expansion are critical.
In view of the above mentioned desired characteristics, the present invention provides an improved adhesive coating for providing a tightly adherent coating for human teeth, for use as a primer in advance of fillings, decorative coatings, and as a sealer to prevent subsequent decay.
Compounds have been developed for providing an adhesive bonding of composite materials to hard tooth tissues. For example, the U.S. Pat. No. 4,521,550 to Bowen, issued June 4, 1985 and 4,588,756 to Bowen, issued May 13, 1986 relate to methods for obtaining strong adhesive bonding of composites to dentin, enamel, and other substrates. The Bowen patents provide a substrate surface that is treated with an aqueous solution of at least one acidic salt containing a polyvalent cation which preferably is capable of changing valence by unit steps and which can bind to dentin or enamel surface sites, and at least one anion which preferably forms a relative water-insoluble precipitate or precipitates with calcium, and which contains at least one carboxyl group and preferably two or more carboxyl groups. After treatement of the surface with a solvent, a final solution is applied.